Containers used for the shipping, storing, and delivery of liquids, such as medical or therapeutic fluids, are often fabricated from single-ply or multi-ply polymer based materials. The materials used to construct the container must be folded or two sheets must otherwise be placed in overlapping relationship and the overlapping sheets bonded at their outer periphery to define a chamber or pouch for containing liquids. Typically, the materials are joined along their inner surfaces using bonding techniques such as heat sealing, radio-frequency sealing, thermal transfer welding, adhesive sealing, solvent bonding, sonic sealing, and laser welding.
For most applications, the seal formed must be of sufficient strength to withstand the stresses generated by dropping, or agitating the liquid filled container. Problems have been encountered in forming sufficiently strong seals in multilayered materials where the components that constitute the material are, in some way, incompatible with one another. One problem that has been encountered is in forming strong seals in multilayered materials that have a large discrepancy in the moduli of elasticity of the material component parts.
For example, a cell culture container described in co-pending and commonly assigned U.S. patent application Ser. No. 08/330,717, is constructed of a multilayered material having an outer layer of a polymer blend of styrene-ethylene-butene-styrene ("SEBS") block copolymer (40%-85% by weight), ethylene vinyl acetate (0-40% by weight), and polypropylene (10%-40% by weight) and an inner layer of a polystyrene. Because of the difference in the moduli of elasticity of the components of the multilayered material, it was not possible to form strong seals by bonding the polystyrene layers to one another. Consequently, the resulting cell culture container was not capable of being centrifuged at useful speeds, and could not in many instances be dropped at heights above six feet without the seals failing.
U.S. Pat. No. 3,403,064 ("the '064 patent") discloses a method of forming a composite plastic container with an inner and outer seal. The walls of the container are laminates each including an inner layer of a polyhalohydrocarbon film and an outer layer of a polyvinyl resin. A pair of the laminates are placed in confronting relation between a pair of dies. This results in a layered structure of four layers between the dies at the commencement of the sealing process. By squeezing the dies and applying inductive sealing energy, such as ultrasonic or radio frequency energy, two seals are formed. An outer seal is formed between the outer layers (polyvinyl resin). The inner layers (polyhalohydrocarbon films) melt and are pushed inward, out of the area of the dies, to form an inner seal 16. The sealing process thus creates two seal areas having different numbers of layers. The outer seal area comprises two layers (two polyvinyl resin layers), and the inner seal area comprises four layers (two polyvinyl resin layers and two polyhalohydrocarbon film layers). The difference in layers is created by forcing the inner layers out of the first seal area during the sealing process. To accomplish this, however, the materials of the inner and outer layers of the '064 patent must have varying responsiveness to exposure to ultrasonic or radio frequencies to allow for relative movement of the layers. This prevents the use of conduction sealing energies.
Other difficulties have been encountered in sealing access ports in the container. In the medical field, as well as in other fields, it is customary to include access ports so that the contents of the container may be accessed from outside the container. The access ports typically have a cylindrical shaped tube of small diameter that extends from outside the container to inside the container to provide a fluid passageway into and out of the container. Sealing of an access port to the side walls of the container using conductive heat sealing techniques however, has led, in an unacceptable number of cases, to what is termed as channel leak. Channel leak is thought to result from an incomplete seal along the outer periphery of the port tube with the sidewalls of the container thereby resulting in a channel that allows fluid to flow from the container along the outer periphery of the port tube.
For some medical applications, such as reconstituting drugs, it is desirable to construct a container with multiple compartments, with each compartment divided along a frangible seal which will rupture when subjected to a certain fluid pressure. For example, medical containers may include more than one compartment, separately containing substances which may be mixed once the frangible seam which divides the compartments is broken. One such type of multiple-compartment container is disclosed in U.S. Pat. No. 5,176,634 ("the '634 patent"). The container of the '634 patent is seamed around the periphery of the two sidewall inner surfaces, and includes a similar seam at an intermediate portion of the container to define two inner compartments. The intermediate seam is frangible ("peelable"). The '634 patent discloses making the periphery seam stronger by using a sealing technique with higher temperature, pressure and time than used to create the peelable seam. However, such a method of making a periphery seam which is sufficiently stronger than an internal frangible seam, while providing a leak proof frangible seam, is difficult and inexact. Slight variations in the sealing parameters in the '634 sealing technique could result in a weak peripheral seam or leakage in the frangible seam. Further, the '634 sealing technique would be ineffective in sealing multilayered materials if the inner layers of the materials were not capable of forming a strong peripheral seal.
Because of the problems discussed above relative to forming a strong peripheral seam in certain multilayered materials there is a need for a creating a suitably strong peripheral seam in such materials. Also, there is a need for an economical and leakproof way of providing an access port or tube which passes from within to outside the container through the container periphery seam. Further, because of the problems discussed above relative to the use of a frangible seam within the container and a container peripheral seam, there is a need for creating a suitable frangible internal seam while providing a peripheral seam which is of much greater strength.